Which substance inhibits intestinal motility?

Epinephrine is the Substance that Inhibits Intestinal Motility

Among the listed options, epinephrine is the substance that inhibits intestinal motility. 1

Evaluation of Each Option

Epinephrine (correct answer)

• Epinephrine has been demonstrated to have the strongest inhibitory effect on intestinal peristalsis among catecholamines 1
• It suppresses intestinal motility through uncoupling of control activity to response activity by suppressing prepotentials in intestinal smooth muscle cells 2
• Epinephrine-induced hyperpolarization of intestinal smooth muscle cells may be due to an increase in potassium permeability, contributing to its inhibitory effect on intestinal motility 2

Other Options (incorrect)

• Gastrin: Primarily stimulates gastric acid secretion and has minimal effects on intestinal motility 3

• Cholecystokinin (CCK): Stimulates rather than inhibits intestinal motility, with its primary functions being gallbladder contraction and pancreatic enzyme secretion 3

• Motilin: Acts as a prokinetic agent that stimulates intestinal motility, not inhibits it 3

  • Motilin receptor agonists like erythromycin are used to enhance gut motility in patients with gastrointestinal motility disorders 4

• Serotonin (5-HT): Generally promotes intestinal motility rather than inhibiting it 3

  • 5-HT4 receptor agonists like prucalopride are used as prokinetic agents to stimulate colonic peristalsis and enhance bowel motility 4

Mechanism of Epinephrine's Inhibitory Effect

• Epinephrine acts on alpha-2 adrenergic receptors in the intestinal smooth muscle to inhibit propulsive motility 5
• The rank order of inhibitory potency among catecholamines is: epinephrine > norepinephrine > dopamine > dobutamine ≈ dopexamine 1
• Epinephrine is approximately 500 times more potent at suppressing peristalsis compared to dobutamine and dopexamine 1

Clinical Implications

• Understanding substances that inhibit intestinal motility is important in managing conditions like:

  • Postoperative ileus 5
  • Diarrheal disorders 6
  • Critical illness requiring catecholamine support 1

• When catecholamine support is needed in critically ill patients, dobutamine and dopexamine may be preferred over epinephrine when preservation of intestinal motility is desired 1